Mono amyl and mono butyl di-hydrogen phosphate additives for synthetic ester lubricans



United States Patent MUNO AMYL AND MON O BUTYL DI-HYDROGEN PHOSPHATE ADDITIVES FOR SYNTHETIC E3- TER LUBRICANTS George W. Eckert, Wappingers Fails, Howard V. Hess,

Glenham, and Charles (I. Towne, Fishltill, N.Y., assignors to Texaco Inc., New York, N.Y., a corporation of Deiaware No Drawing. Filed June 22, 1960, Ser. No. 37,862

3 Claims. (Cl. 252-498) This invention relates to an improved lubricating composition containing an additive which exhibits very high extreme pressure properties. More particularly, this invention relates to synthetic oils containing mono amyl or mono butyl (ii-hydrogen phosphate compounds as extreme pressure additives.

There is an ever increasing need for the improvement of the extreme pressure properties of lubricating oils used in high speed machinery. This is particularly true for the lubrication of newly developed jet turbine engines. The present invention defines an additive possessing extreme pressure action which is particularly useful in the formation of jet engine lubricants.

The present invention consists essentially of a synthetic carboxylic acid ester base lubricating oil containing from 0.1 to 5.0 volume percent of at least one alkyl dihydrogen phosphate selected from the group consisting of mono amyl and mono butyl di-hydrogen phosphate. These low concentrations of mono amyl and mono butyl di-hydrogen phosphates cause a very significant and substantial improvement in the extreme pressure properties of synthetic lubricating oils.

It is well known that phosphate esters are used as extreme pressure additives for lubricating oils. This invention involves the discovery that mono amyl and/or mono butyl di-hydrogcn phosphates impart unexpected and outstanding extreme pressure properties to synthetic ester lubricating oils. This is extremely significant in the light of the present invention in that these same acid phosphates, herein described, demonstrate no significant improvement in extreme pressure properties over other phosphate esters when employed in mineral oils.

The concentration of the mono alkyl di-hydrogen acid phosphates employed in the lubricant compositions of the present invention, as stated above, falls between about 0.1 to 5 .0 volume percent of the total lubricant with concentrations between about 0.1 and 3.0 volume percent with the most desirable concentration 1.0 volume percent.

The esters which constitute the major portion of the lubricant composition of this invention are broadly described as esters of hydroca-rbyl carboxylic acids. They are high molecular weight materials of lubricating oil characteristics derived from alcohols which are usually aliphatic alcohols containing 1 or more hydroxyl radicals, and monocarboxylic acids which are usually aliphatic carboxylic acids containing 1 or more carboxylic acid radicals.

Widely used synthetic ester lubricants are aliphatic diesters of aliphatic dicarboxylic acids containing 612 carbon atoms. From the standpoint of cost and availability, the preferred dibasic acids are adipic acid, sebacic acid and azelaic acid. The aliphatic alcohols used to form the diesters usually contain at least 4 carbon atoms and up to 20 or more carbon atoms. C to C alcohols are most commonly used. Ether alcohols such as Cellosolve and Carbitol may also be used in the formation of the aliphatic diesters of organic dicarboxylic acids used as the lubricating base in the compositions of this invention. Alcohols containing 2 or more hydroxyl radicals and no hydrogen substituted on the beta carbon atom such as trimethylol propane and pentaerythritol have proven 3 9 71 Patented July 9, 1963 particularly eifective in formulating stable high temperature ester lubricants.

Examples of alkyl esters of aliphatic carboxylic acids are the following: di-isooctyl azelate, di-Z-ethylhexyl sebacate, di-Z-ethylhexyl azelate, di-2-ethylhexyl adipate, dilauryl azelate, di-sec-amyl sebacate, di-Z-ethylhexyl alkenylsuccinate, di-2-ethoxyethy1 sebacate, di-2-(2-rnethoxyethoxy) ethyl sebacate, di-2-(2'-ethylbutoxy) ethyl sebacate, di-2-butoxyethyl azelate, di-2-(2'-butoxyethoxy) ethyl alkenyl-succinate, pentaerythritol tetracaproate and trimethylol propane tri-isooctanoate.

In addition to such esters, polyester lubricants formed by a reaction of an aliphatic dicarboxylic acid, a dihydroxy compound and a monofunctional compound, which is either an aliphatic monohydroxy alcohol or an aliphatic monocarboxylic acid, in specified mol ratios are also employed as the synthetic lubricating base in the compositions of this invention; polyesters of this type are described in US. 2,628,974 on Polyester Synthetic Lubricants, which issued to R. T. Sanderson on February 17, 1953. Polyesters formed by reaction of a mixture containing specified amounts of 2-ethyl-1,3-hexanediol, sebacic acid, and 2-ethylhexanol and by reaction of a mixture containing adipic acid, diethylene glycol and 2- ethylhexanoic acid illustrate this class of synthetic polyester lubricating bases.

The sulfur analogs of the above-described esters are also used in the formulation of the lubricating compositions of this invention. Dithioesters are exemplified by di-Z-ethylhexyl thiosebacate, di-n-octyl thioadipate and the dilaurate of 1,5-pentanedithiol; sulfur analogs of polyesters are exemplified by the reaction product of adipic acid, thioglycol and 2-ethylhexyl mercaptan.

Alkyl-substituted phenols are usually incorporated in the lubricants of the invention as anti-oxidants. The preferred and most commonly used alkyl phenol antioxidants are 2,6-di-tertiary octylphenol; 2,6-di-tertiary amyl-4-methylphenol; and 2,6-di-isopropyl-4-methylphenol. Hindered phenols of this type are employed in concentrations between 0.1 and 1.0 weight percent.

Although hindered phenol type anti-oxidants are the most Widely used anti-oxidants in the lubricant compositions of the invention, aryl-substituted amine anti-oxidants such as phenylnaphthylamine, phenylene diamine, and diphenylarnine are also used in lubricants in conjunction with the extreme pressure additive of the invention. The amine anti-oxidants are employed in the same concentrations as the hindered phenol anti-oxidant.

Organic silicones are normally incorporated in the lubricants of the invention to impart thereto anti-foam properties. The silicones are usually of the dialkyl or mixed alkyl-aryl silicone type. Dirnethyl silicone is normally employed as the anti-foam agent. The silicone is incorporated in the lubricant by means of a kerosene concentrate containing 5 to 15 weight percent silicone. A very satisfactory anti-foam agent is a kerosene concentra-te 10 weight percent dimethyl silicone. The kerosene concentrate is employed in an amount sufficient to provide a silicone polymer concentration of from 50 to 250 parts per million based on the total lubricant composition.

Various alkyl acid phosphate compounds were evaluated in both mineral and synthetic lubricating oils in a number of concentrations in the mean Hertz load test. The procedure and apparatus of this test is described in US. Patent 2,600,058.

The base oils that Were used in the mean Hertz load test for evaluating the additives of the present invention were the following:

A parafiin base residum having an SUS viscosity at 210 F. of between and and which had been subjected to refining sequence comprising propane deas phalting, furfural refining, solvent dewaxing and clay filtering and hereafter designated as Base Oil A;

Di-Z-ethylh'exyl sebacate hereafter designated as Base Oil B;

A distillate mineral oil, paraffin base having an SUS 5 viscosity at 100 'F. of between 300 and 324 and hereafter designated as Base Oil C.

In Table I following are shown data indicating the superiority of the mono amyl and mono butyl di-hydrogen phosphate additives of the present invention in the mean Hertz load test in ester base lubricating oils. The base oils are those described immediately above.

Table I 1 Mean 5 Example 011 and Volume Percent Additive Hertz Load Base Oil A Base Oil A plus 1.0% triethyl phosphate 21 2 Base on A plus 1.0% mixture ofmono and di-octyl 24 0 hydrogen phosphates. Base Oil A plus 1.0% mono-lauryl phosphate 1. 31 Base Oil A plus 1.0% octyl-di-hydrogen phosphate 24 Base Oil A plus 1.0% mono-stearyl di-hydrogen 26 phosphate. Base Oil A plus 1.0% mono-amyl-di-hydrogen 32 phosphate. Base Oil B 19 Base Oil B plus 1.0% trieresyl phosphate" 30 Base Oil B plus 1.0% triethyl phosphate 25 Base Oil B plus 1.0% mixture of mono-di-octyl 31 hydrogen phosphate. Base Oil B plus 1.0% mono-lauryl di-hydrogen 39 phosphate. Base Oil B plus 1.0% oetyl di-hydrogen phosphate..- 37 30 Base Oil B plus 1.0% mono-amyl (ii-hydrogen 127 phosphate. Base 011 B plus 0.1% mono-amyl di-hydrogen 49 phosphate. Base Oil B plus 0.1% mono-butyl (ll-hydrogen 52 phosphate. Basle 0% B plus 0.5% mono-butyl di-hydrogen 98 p osp ate. Basle 0% B plus 0.75% mono-butyl di-hydrogen 121 p osp ate. Base Oil B plus 1.0% mono-butyl (ll-hydrogen 123 phosphate. Base Oil 0 14 Base Oil 0 plus 1.0% trieresyl phosphate 13 Base Oil 0 plus 1.0% oetyl (ll-hydrogen phosphate 25 Base 0111 $3 plus 1.0% mono-lauryl (ii-hydrogen 31 p osp a e. Base Oil 0 plus 1.0% mono-amyl (ii-hydrogen 30 phosphate.

The data of the foregoing table clearly demonstrates that mono amyl and butyl (ii-hydrogen acid phosphates as described herein promote unexpected and improved extreme pressure activity in synthetic ester base lubricants. The addition of no additive to the base oils tested gave a reading of 20, 19 and 14 in Examples 1, 8 and 20 respectively. The addition of various higher alkyl acid phosphate compounds including the mono-amyl di-hydrogen phosphate of the present invention in ranges up to 1.0 percent in Base Oils A and C gave readings of up to about 30-37: Examples 2 7 and 21-24. However, when the mono amyl and butyl di-hydrogen acid phosphates were added in from 0.1 to 1.0 volume percent to the synthetic ester base oil, Base Oil B, the reading ranged from 49 to 123, examples 14 to 19. It is especially significant that the addition of 1.0% of other alkyl acid phosphates fail to increase the mean Hertz load above 39 in the synthetic ester base oils. This, therefore, obviously indicates the unexpected results that are obtained by the use of the mono-amyl and mono-butyl di-hydrogen phosphate additives for synthetic ester base lubricants.

We claim:

1. A synthetic aliphatic dicarboxylic acid aliphatic diester base lubricant containing from 0.1 to 5.0 volume pe cent of an alkyl acid phosphate selected from the group consisting of mono-amyl di-hydrogen phosphate, monobutyl di-hydrogen phosphate and mixtures thereof.

2. The lubricating composition of claim 1 wherein said alkyl acid phosphate is present in 1.0 volume percent.

3. A lubricating oil composition according to claim 1 in which said synthetic aliphatic dicarboxylic acid aliphatic diester base is di-Z-ethylhexyl sebacate.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A SYNTHETIC ALIPHATIC DICARBOXYLIC ACID ALIPHATIC DIESTER BASE LURBICANT CONTAINING FROM 0.1 TO 5.0 VOLUME PERCENT OF AN ALKYL ACID PHOSPHATE SELECTED FROM THE GROUP CONSISTING OF MONO-AMYL DI-HYDROGEN PHOSPHATE, MONOBUTYL DI-HYROGEN PHOSPHATE AND MIXTURES THEREOF. 